1. Technical Field
The invention relates generally to semiconductor packaging and chip design, and, more specifically, to a wire structure and construction method for stacked chip modules and packaging of semiconductor chips containing very large scale integrated circuit (VLSI) circuits, such as microprocessors and associated memory.
2. Related Art
Flip-chip module technology has facilitated increased system density and also increased operating frequency by reducing interconnection distances and increasing signal propagation speed. As chip operating frequencies and power dissipation requirements increase, it has become more difficult to make low impedance power supply connections to a chip or chips. Historically, Controlled Collapse Chip Connection (C4) flip-chip structures have had much better power distribution than wire bond designs, because the C4 chip carrier is typically designed with power supply planes in the chip carrier which can be connected to the chip in many places by C4 solder bumps (usually in a ball grid-array). Wire bonded chips are not as attractive for power distribution because they usually have just peripherally-located pads, and thus power must be distributed within the chip by only the internal chip wiring, which results in higher impedance and increased susceptibility to supply line noise.
Recently, stacked chip packages have begun to be used in industry since they allow for high bandwidth interconnects between multiple chips of potentially dissimilar technologies. The goal of moving to System-On-a-Chip (SoC) technologies may actually, in many cases, be less costly to implement as System-On-a-Package (SoP) technology. Flip-chip, or other stacked chip arrangements, offer the best high bandwidth chip-to-chip interconnects, but suffer from power distribution problems similar to the wire bond chip situation described above.
Accordingly, there exists a need in the industry for a low impedance power distribution structure, for use in flip-chip type stacked chip modules, which is capable of solving the above-mentioned problems resulting from high impedance wires in power distribution circuits.
It is therefore a feature of the present invention to overcome the above shortcomings related to flip-chip type stacked chip module power distribution structures, by providing a method and structure for a low impedance power distribution wire structure.
In a first general aspect, the present invention provides a wire structure made from an under bump metallurgy (UBM) process, said wire structure comprising: a substrate having a plurality of first features, said first features including under bump metallurgy; a plurality of second features situated over at least one of said first features, said second features operatively connected to said first features; at least one electrical wire interconnecting said plurality of first features, wherein said electrical wire includes under bump metallurgy, said electrical wire comprising a metal structure having a low impedance and characterized by having substantially the same composition as the contact pads; and wherein said first features and said electrical wire are formed in substantially the same plane.
In a second general aspect, the present invention provides an electronic package comprising: a first substrate having a first surface, said first surface including a plurality of first features; a second substrate having a second surface, said second surface including a plurality of second features, wherein said second substrate is positioned substantially parallel to said first substrate, and wherein said second surface is located proximal to and facing said first surface; first electrical wires located on said first surface, said first electrical wires connecting selected ones of said plurality of first features on said first surface; second electrical wires located on said second surface, said second electrical wires connecting selected ones of said second plurality of second features on said second surface; wherein said first substrate and said second substrate are operationally bonded together; and said first electrical wires, said second electrical wires, said first features and said second features are formed with under bump metallurgy (UBM) processing.
In a third general aspect, the present invention provides a method of forming an electronic package comprising: providing a first substrate having a first surface, said first surface including a plurality of first features; providing a second substrate having a second surface, said second surface including a plurality of second features, wherein said second substrate is positioned substantially parallel to said first substrate, and wherein said second surface is located proximal to and facing said first surface; providing first electrical wires located on said first surface, said first electrical wires connecting selected ones of said plurality of first features on said first surface; providing second electrical wires located on said second surface, said second electrical wires connecting selected ones of said plurality of second features on said second surface; wherein said first substrate and said second substrate are operationally bonded together; and forming said first electrical wires, said second electrical wires, said first features, and said second features with under bump metallurgy (UBM) processing.
The foregoing and other features and advantages of the invention will be apparent from the following more particular description of embodiments of the invention. It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention.